1. Field of the Invention
This invention relates to a rotary connector for connecting relatively rotatable members.
2. Description of the Related Art
Among various rotary connectors for connecting relatively rotatable members, a rotary connector used in an automotive air bag is known, for example. This type of rotary connector comprises a fixed case constituted by a base plate and an outer cylindrical case, an inner cylindrical case (rotatable case) rotatably coupled with the fixed case, and a flexible flat cable wound in spiral form and arranged in an annular space defined by the fixed and rotatable cases. Each of the cases is produced by molding a synthetic resin.
This rotary connector is required to provide smooth rotation for a long time after it is mounted to an automotive vehicle. To this end, in conventional rotary connectors, a small clearance is defined between the rotatable case and the fixed case, to prevent the interference between the cases and thereby ensure smooth rotation. For example, in a conventional arrangement, a clearance extending vertically along the axis of rotation of the rotary connector is provided at a portion at which the lower part of the inner cylindrical case engages the base plate.
Usually, however, rotary connectors of this type are fixed to a vehicle body side with a steering column passed through the center of the inner cylindrical case serving as the rotatable case. Accordingly, if a clearance extending along the axis of rotation exists between the base plate and the inner cylinder case, grease or dust is likely to enter the case from parts arranged nearby, such as a combination switch, due to vibration of the vehicle body.
Grease or dust that has entered the case adheres to the base plate, inner cylindrical case, flat cable, etc., and smooth rotation of the rotary connector is hindered after long use.